Thanks everyone ... The vignette of the picture is not intentional. I think I may try to correct it. I believe it was a result of a 17mm focal length + wider aperture + CPL.

You know, it was hard to take a picture of it without a single person in the photo at that time. This thing is pretty cool. But it attract a lot of kids. So I think I was lucky to take a photo without anyone standing in front of it.

Here is another shot from a different angle so you know what it really looks like.